The present invention is directed to an improved process for the copolymerization of epoxides with carbon dioxide.
Epoxides are known to copolymerize with carbon dioxide, with metal containing catalysts such as zinc diethyl with additives, zinc dicarboxylates, and metal porphyrin complexes.
The resulting copolymers have alternating epoxide and carbon dioxide groups, and are polycarbonates. These copolymers have found uses in many areas, such as ceramic binders, evaporative pattern casting and adhesives. Epoxides shown to proceed readily in this reaction are ethylene oxide, propylene oxide, cyclohexene oxide, cis-2-butene oxide, and others.
When zinc dicarboxylates are used as catalysts, the required quantity is usually fairly high, due to their relatively low activities under the reaction conditions. This creates some undesirable side effects, such as catalyst removal and added costs. It is therefore desirable to increase the activity of the catalysts, thus producing the polymers at lower costs.